In the production of fire retardant felted mineral fiber panels, an aqueous slurry typically comprising mineral wool, clay and starch is dewatered on the screen of a Fourdrinier machine. U.S. Pat. No. 3,510,394 discloses the use of flocculent materials in the water to prevent the dispersal and loss of starch and clay with the drainage water.
The prior art contains numerous examples of mechanically produced aerated foam in the aqueous slurry. The foam prevents the stratification of materials during drainage. Although the foam successfully retains the particles in a space matrix without significant stratification, the presence of mechanically produced foam increases water drainage time beyond the limits of practical production rates.